Engineers with the National Highway Traffic Safety Administration drove a 2008 Prius allegedly involved in an incident of unintended acceleration last week in California, but have found no evidence either to support or disprove the driver's claims about the incident.

The driver, James Sikes, 61, called 911 after he lost control of the vehicle on the freeway. "So far, we have not been able to find anything to explain the incident that Mr. Sikes reported," said an NHTSA statement. "We would caution people that our work continues and that we may never know exactly what happened with this car."

Sikes was driving near San Diego on Monday, March 8, 2010 when the Prius sped out of control while he was passing another car. The Prius reached speads of more than 90 mph before police helped Sikes bring the car to a stop by applying the gas and brake pedals simultaneously. The incident lasted approximately 20 minutes, during which time Sikes traveled approximately 30 miles.

Both NHTSA investigators and representatives from Toyota are examining the vehicle via direct driving tests and through diagnostic readout obtained from the data recorder on the vehicle.

When the officer helped Sikes out of the car, the brake pads were smoking and the NHTSA report mentioned that the pads "were completely gone."